Topic: My AcuRite instrument giving high readings in the daytime

[neptune]

I live in a rural area.  I have an instrument shelter in my back yard, which houses my my AcuRite temperature instrument.  The shelter is built of wood and ventilated.  It is in the middle of my back yard, about 20-30 feet away from the house, and is not underneath any trees.  The nearest NOAA station is in town, about 5 miles away.

Here's my dilemma.  In the daytime, my highs are usually several degrees higher than those of the nearest NOAA stations.  However, at night, this is not the case, and in fact my readings are usually lower, often by several degrees.  I would expect that, since I live in a rural area.  But what explains the high daytime readings?  For instance, the highest temperature I recorded for August was 96.  However, the highest reading of the NOAA station about 5 miles away for August was 91, I believe. 

So, what would explain these discrepancies?  Is it the instrument, or something else?  Thanks for any info. 

[wxman2003]

I live in a rural area.  I have an instrument shelter in my back yard, which houses my my AcuRite temperature instrument.  The shelter is built of wood and ventilated.  It is in the middle of my back yard, about 20-30 feet away from the house, and is not underneath any trees.  The nearest NOAA station is in town, about 5 miles away.

Here's my dilemma.  In the daytime, my highs are usually several degrees higher than those of the nearest NOAA stations.  However, at night, this is not the case, and in fact my readings are usually lower, often by several degrees.  I would expect that, since I live in a rural area.  But what explains the high daytime readings?  For instance, the highest temperature I recorded for August was 96.  However, the highest reading of the NOAA station about 5 miles away for August was 91, I believe.  

So, what would explain these discrepancies?  Is it the instrument, or something else?  Thanks for any info.  

Have you tried a regular thermometer for comparison? Is your shelter painted white? How is it ventilated? How is the Acurite rated for accuracy? It should be listed on their site +/- X amout degrees. NWS ASOS readings are considered within specs if temperatures are within 4 degrees with test equipment. Generally though they are calibrated within 1 degree. Also, the surrounding vegetation of the ASOS will affect temperature. When I worked at NWS before retirement this spring, it was not unusual that the temperature in the instrument shelter at the office to be 3 to 5 degrees warmer than the ASOS 1 mile away during the summer months. The ASOS was located near an alfalfa field which was green and kept daytime highs cooler. So many variables, that the only way to know for sure is to compare your readings with another accurate thermometer on site, side by side.

[SLOweather]

So, what would explain these discrepancies?  Is it the instrument, or something else?  Thanks for any info. 

Microclimates, distance, elevation, inversion layers... Temperature is one of the most variable of the measured weather parameters. On our property, the temperature can vary by >10F over a distance of 300' and elevation change of 100'. It's not surprising that you are seeing those variances over those distances.

[DanS]

in addition to wxman2003 " Is your shelter painted white? How is it ventilated? "
Also, the ground cover surrounding and nearby the shelter can make a difference. Ideally, low and cut grass all around and away from anything else such as concrete, asphalt, gravel, wood, brick, etc.

[neptune]

Have you tried a regular thermometer for comparison?

Do you mean a wall-type, non-digital one?

Is your shelter painted white?

Yes.  Here's the kind I have:

http://www.benmeadows.com/instrument-shelter_s_53738/
 

How is the Acurite rated for accuracy? It should be listed on their site +/- X amount degrees.

I'm not sure.  Does the accuracy listed on their Web site vary according to what part of the range you're checking?  As I said, these inflated temps only occur during the day--never at night.

it was not unusual that the temperature in the instrument shelter at the office to be 3 to 5 degrees warmer than the ASOS 1 mile away during the summer months.

That's interesting.

So many variables, that the only way to know for sure is to compare your readings with another accurate thermometer on site, side by side.

I see.  Thanks for the info.

[neptune]

Temperature is one of the most variable of the measured weather parameters. On our property, the temperature can vary by >10F over a distance of 300' and elevation change of 100'.

Wow!

It's not surprising that you are seeing those variances over those distances.

Well, the one thing that's fairly constant is that my daytime readings are higher than the neighboring NOAA stations' readings in the summer.  Incidentally, looking at Weather Underground, I've noticed that most nearby personal weather stations give higher daytime readings (often much higher) than those of the surrounding NOAA stations.  So apparently a lot of folks experience this.

[neptune]

Also, the ground cover surrounding and nearby the shelter can make a difference. Ideally, low and cut grass all around and away from anything else such as concrete, asphalt, gravel, wood, brick, etc.

That pretty much describes my ground cover--low-cut grass, and the shelter is not that close to any concrete, asphalt, gravel, wood, brick, or anything similar.  It's also mounted about 5 feet off the ground. 

[DanS]

"Here's the kind I have:
http://www.benmeadows.com/instrument-shelter_s_53738/  "

Maybe the instrument's position in the shelter results in it reading the wood warming from the sun? Especially if it's mounted on the back wall and the sun is hitting that side. You could try placing the instrument on the floor, in the center, for a couple days. Being on the floor also gets it out of any possible trapped heat nearer to the top of the shelter.

[BigOkie]

"Here's the kind I have:
http://www.benmeadows.com/instrument-shelter_s_53738/  "

Maybe the instrument's position in the shelter results in it reading the wood warming from the sun? Especially if it's mounted on the back wall and the sun is hitting that side. You could try placing the instrument on the floor, in the center, for a couple days. Being on the floor also gets it out of any possible trapped heat nearer to the top of the shelter.

Saw this in the description:

"Instrument Shelter provides tamper-free storage of thermometers, temperature and weather instruments. Sloped roof promotes precipitation run-off. Hinged door, louvered front and sides resist the elements. Interior mounting block prevents hanging instruments from touching the back wall. Includes a lock with two keys for security."

Are the instruments mounted on the block?

[Weather Display]

the acu rite relies on the solar powered fan to draw air in and over the internal sensor to give a reprenstative reading
ideally in my opinion it should have its an instrument shelter like the Davis VP for the temp/hum
(as yes it does tend to read too high)
you you could build your own and then remove the temperature sensor from the acu rite station, and run wires to your instrument shelter (i.e lengthen the wire)
?

[nincehelser]

I haven't seen where the type of Acurite "instrument" is discussed.  It could be a plain old thermometer, a wired sensing element, or a wireless sensor. 

Can you provide a model #?

On the assumption that it is a tower sensor, my gut feel is that the enclosure is too small to permit proper airflow.  The tower sensor should be mounted exposed to the outdoors, yet shielded from the sun and rain.

You might try leaving the enclosure door open, or if the louvers are adjustable, open them up as much as possible.

I'm just thinking an enclosure within an enclosure might be just a little too much.

[neptune]

Maybe the instrument's position in the shelter results in it reading the wood warming from the sun? Especially if it's mounted on the back wall and the sun is hitting that side. You could try placing the instrument on the floor, in the center, for a couple days. Being on the floor also gets it out of any possible trapped heat nearer to the top of the shelter.

Thanks--those are good suggestions.

[neptune]

Are the instruments mounted on the block?

I have a string with a hook that I've attached the sensor to.   So, the sensor is hanging in the middle of the shelter, not touching anything but the hook.

Incidentally, I opened the shelter yesterday to stick a "regular" thermometer in it and there was a wasp's nest.     The regular thermometer did agree with the sensor, though--both said 87 degrees.

[neptune]

the acu rite relies on the solar powered fan to draw air in and over the internal sensor to give a reprenstative reading

Maybe you're referring to a more deluxe model.  Mine is pretty basic.

ideally in my opinion it should have its an instrument shelter like the Davis VP for the temp/hum
(as yes it does tend to read too high)
you you could build your own and then remove the temperature sensor from the acu rite station, and run wires to your instrument shelter (i.e lengthen the wire
)

Yes, another shelter probably would work better for me.

[neptune]

I haven't seen where the type of Acurite "instrument" is discussed.  It could be a plain old thermometer, a wired sensing element, or a wireless sensor.  

Can you provide a model #?

It's a wireless sensor.  I looked on the back and it said "00611  Made in China."  Given the source, perhaps some inaccuracy should be expected.  

On the assumption that it is a tower sensor, my gut feel is that the enclosure is too small to permit proper airflow.  The tower sensor should be mounted exposed to the outdoors, yet shielded from the sun and rain.

You might try leaving the enclosure door open, or if the louvers are adjustable, open them up as much as possible.

The louvers aren't adjustable, but leaving the door open might help.  Anyway, I think you and the other posters have the right idea that the instrument shelter may be the biggest cause of the skewed readings.

Thanks for all the replies.

[Weather Display]

oh, mad bad, I had presumed it was a 5 in 1 station

[Rhino]

The 00611 sensor reads temperature only, accuracy is +/- 2º.

If it is mounted in a well ventilated area out of direct sunlight and away from vegetation, it will be pretty accurate.

[neptune]

oh, mad bad, I had presumed it was a 5 in 1 station

Oh, no problem.  I guess most folks on here have splurged for ritzier options than me.   

[neptune]

The 00611 sensor reads temperature only, accuracy is +/- 2º.

Thanks for the info.

If it is mounted in a well ventilated area out of direct sunlight and away from vegetation, it will be pretty accurate.

I suspect that "well-ventilated" might be the issue, and perhaps the size of the shelter.  Those would seem to be the only logical explanations for why my readings are usually lower than the nearby NOAA readings at night but higher during the day.  Actually, I think my nighttime readings are accurate, because I live out in the country, where it naturally would be a bit cooler at night.  It seems my daytime readings are often 5 or 6 degrees higher, though.  For instance, yesterday I recorded a high of 92, but I think the closest NOAA (about 5 miles away) had a high of either 86 or 87.  The other NOAAs (1 to 2 hours away) had similar readings in the upper 80s.  

And right now, as we speak, I have a reading of 65, while the closest NOAAs range from 67 to 70+. 

[DanS]

Is there any way that you could share a few pictures of the shelter's location and it's surroundings? It may help.

[neptune]

Is there any way that you could share a few pictures of the shelter's location and it's surroundings? It may help.

Sure, I'll try to snap a few. 

[neptune]

OK, here are a few sexy photos of my instrument shelter:

http://s1104.photobucket.com/user/panettonea/library/Instrument_shelter?sort=2&page=1

Unfortunately, I forgot to open up the shelter and get a picture of the wasp's nest inside, but hopefully no one will be too disappointed. 

[DanS]

Well location in the yard and height from the ground all look ideal. I'd tend to think that if the instrument isn't mounted up near the top and isn't touching any sunlit sides then those readings are the temperatures around there at that time, regardless what any stations are reading 5 miles down the road.

[miraculon]

neptune,

That last photo shows what appears to be a shingle over the top. In the other photos, it seems to be more white, but in the last one it seems gray.

I assume that you are trying to protect the wood. Have you run it without the shingle? Could you paint the shingle white?

It might be absorbing some solar energy and heating the enclosure.

Greg H.

[neptune]

Well location in the yard and height from the ground all look ideal. I'd tend to think that if the instrument isn't mounted up near the top and isn't touching any sunlit sides then those readings are the temperatures around there at that time, regardless what any stations are reading 5 miles down the road.

OK, thanks--that's good to hear, Dan.     Why temps would be higher in a rural area...well, who knows.